This paper develops the Latent Symmetric Elasticity Structure (LSES), a market share price elasticity model which allows elasticities to be decomposed into two components: a symmetric substitution index revealing the strength of competition between brand pairs, and a brand-specific coefficient revealing the overall impact of a brand on its competitors. An application of the model to unconstrained cross price elasticities shows that brand-price competition in one market is well-represented by a LSES model in which brand substitutability and elasticity asymmetry are related to average price level.